二次回归正交旋转组合设计优化香蕉浆护色工艺

探索香蕉浆生产过程中护色工艺,为香蕉浆护色条件的选择提供科学依据。采用二次回归正交旋转组合设计方法对香蕉打浆过程中柠檬酸、D-异抗坏血酸钠等护色剂添加量和加水量对香蕉浆护色效果的影响进行研究,优化香蕉浆护色工艺。试验范围内各因素对香蕉浆护色作用大小依次是柠檬酸添加量>抗坏血酸添加量>加水量。根据拟合方程得到香蕉浆护色最佳工艺条件为柠檬酸添加量为0.50%,抗坏血酸添加量为0.10%,水果肉比保持在0.90,理论上在此条件下所得香蕉浆褐变指数69.78。采用此条件对香蕉浆进行护色试验,得到香蕉浆的褐变指数为68.46,与优化理论值相对误差为1.89%,说明此结果具有实际应用价值。     

Ascorbate-2-sulfate as a dietary vitamin C source for atlantic salmon (Salmo salar): 1. Growth,bioactivity, haematology and humoral immune response

The present experiment shows that ascorbate-2-sulfate (AS) is not equivalent to ascorbic acid (AA) as a dietary vitamin C source for Atlantic salmon (Salmo salar). Within reasonable feed supplemental levels AS does not provide the tissues with adequate supplies of vitamin C to secure optimal physiological functions as demonstrated by biochemical and haematological analyses. AS could not be detected in the liver of fish fed either AA or AS, nor in vitamin C — deprived salmon, suggesting that AS is not the natural storage form of vitamin C in this species. There were no significant differences in antibody production against a soluble artificial antigen (NIP₁₁-LPH) in fish fed 500 and 5000 mg AA/Kg dry diet or equivalent amounts of AS during a period of six weeks at a water temperature of 7.2°C.     

Photosynthetic characteristics and protective mechanisms against photooxidation during high temperature stress in two citrus species

Exposure of Satsuma mandarin (Citrus unshiu Marc.) and Navel orange (Citrus sinensis Osbeck) plants to high temperature (38 °C) led to reductions of the net photosynthetic rate (Pn), the photorespiration rate (Pr), the quantum efficiency CO₂ assimilation (ΦCO₂${\Phi }_{\text{C}{\text{O}}_2}$), the maximal photochemical efficiency of PS2 (Fv/Fm), the photochemical quenching (qP) and the quantum efficiency of PS2 photochemistry (Φ_PS2), whereas the minimal fluorescence yield (Fo) and the non-photochemical quenching (qN) increased. Increase in the value of Pr/Pn and ΦPS₂/ΦCO₂${\Phi }_{\text{PS}2}/{\Phi }_{\text{C}{\text{O}}_2}$ was attributed to the greater decrease in Pn and ΦCO₂${\Phi }_{\text{C}{\text{O}}_2}$ than Pr and Φ_PS2. In addition, the superoxide radical (O₂⁻) production, the H₂O₂ concentration and the activities of antioxidant enzymes such as the superoxide dismutase (SOD, EC 1.15.1.1), the ascorbate peroxidase (APX, EC 1.11.1.11), the dehydroascorbate reductase (DHAR, EC 1.8.5.1) and the catalase (CAT, EC 1.11.1.6) were raised. On the other hand, the chlorophyll concentration in leaves decreased during high temperature stress. These results suggest that decline in Pn related to inactivation of PS2 reaction centers may be due to the enhanced number of active oxygen species in the citrus leaves. The water–water cycle may play a role in limiting the degree of photodamage caused by high temperature. Lower O₂⁻ production rate, the H₂O₂ concentration and the antioxidant enzymes activity were observed in high temperature tolerant species of citrus. The exogenous active oxygen scavenger ascorbic acid (Asc) enhanced the ability to clear the O₂⁻ in citrus plants, and quicken the recovery of photosynthetic apparatus.     

杂交小麦抗坏血酸过氧化物酶基因克隆及其在种子老化中的潜在功能分析

以BS型二系杂交小麦BS1453/11GF5135及其BS1453(母本)、11GF5135(父本)的种子为材料,在BS1453/11GF5135中通过同源克隆获得抗坏血酸过氧化物酶基因TaAPX。该基因包含一个832 bp的ORF,共编码277个氨基酸。通过进一步生信分析预测miRNA与TaAPX基因的互作关系,发现TaAPX基因可能受miR396等抗逆及种子活力相关miRNAs的调控。另外通过蛋白互作预测分析,发现APX蛋白主要与氧化还原相关的酶互作反应。通过对不同老化时间的父母本及杂交种的胚进行qPCR及酶活性分析,发现TaAPX基因在杂交种及亲本中的表达趋势是先被诱导上调表达,后下调表达,但杂交种子内TaAPX基因的表达量在第7天才开始下降,而亲本种子内TaAPX基因的表达量在第5天开始下降,且miR396与TaAPX互为拮抗作用。随着老化时间的延长,亲本种子内APX酶活性表现为下降趋势,杂交种子内APX酶活性在第3天呈短暂下降趋势,随后上升,第9天开始下降,表明在老化条件下杂交种子内APX酶清除体内过氧化物的能力高于亲本,即杂交种抗老化能力高于其父母本,且TaAPX基因对种子...     

二氯苯醚菊酯对黄瓜叶片几种氧化酶活性的影响

研究结果表明,二氯苯醚菊酯（PER）对黄瓜几种氯化酶活性有不同程度的影响,其影响的程度与PER的浓度有关。20－40mg.L^-1的PER分别使黄瓜体内的过氧化氢酶和乙醇酸氧化酶活性升高3．35％－32．71％和4．42％－34．51％,20－20mg.L^-1的PER使过氧化物酶活性升高9．70％－29．10％;50－250mg.L^-1的PER使吲哚乙酸氧化酶活性升高13．58％－32．10％;50－300mg.L^-1的PER使抗坏血酸氧化酶活性下降,3．18％－20．69％,用200mg.L^-1的PER处理黄瓜幼苗1－6d后,体内过氧化物酶活升高10．375－43．17％。     

抗虫棉品系L22依赖抗坏血酸H2O2清除酶系统活性的降低

以早衰型转 Bt基因抗虫棉 L2 2为主要试材 ,研究了其体内活性氧代谢和一些抗氧化酶活性与对照常规棉 JM1 1、抗虫棉 33B的差异。结果表明 ,抗虫棉 L 2 2在生长中期时叶片中 H2 O2 含量和膜脂过氧化产物丙二醛 ( MDA)显著增高 ,在依赖抗坏血酸 ( As A)的 H2 O2 清除酶系统中 ,抗坏血酸过氧化物酶 ( As A- POD)、脱氢抗坏血酸还原酶 ( DR)、谷胱甘肽还原酶 ( GR)等酶活性极显著低于常规棉 JM1 1和 33B,叶片中 As A含量也以 L2 2为最低 ,而 DAs A/As A是最高的 ,分别是JM1 1和 33B的 3.75倍和 4.31倍。初步认为 L2 2出现早衰现象与其体内活性氧代谢失调和依赖As A的 H2 O2 清除酶系统活性显著降低有关 ,并分析了可能的原因     

过量表达OsAPX1基因增强水稻的抗热和抗氧化能力

抗坏血酸过氧化物酶(ascorbate peroxidase, APX)是植物体内活性氧清除的关键酶,在植物逆境应答中发挥着重要作用。通过构建水稻OsAPX1基因的过表达植物载体,利用根癌农杆菌介导法导入水稻品种日本晴获得转基因植株。半定量RT-PCR分析表明,转基因植株中OsAPX1表达水平明显提高。田间T0代过表达转基因植株在高温条件下的秕谷率显著低于野生型。热激胁迫实验显示,转基因株系比野生型具有更强的耐热性。在过氧化氢胁迫下,转基因植株也表现出更强的抗氧化能力。该结果表明水稻OsAPX1基因在活性氧清除中发挥功能,过量表达OsAPX1能够增强水稻的高温抗性。